Square balers are agricultural machines that pick up a swath or windrow of crop material, such as straw or hay, from the ground and compact it into bound bales. The crop material is picked up into an infeed housing or chute from which it is conveyed by a feed mechanism, termed a stuffer, through an inlet to a baling chamber. The baling chamber is defined by four walls that are surrounded and supported by a rigid frame. In the baling chamber, the crop material is urged rearwardly by a reciprocating plunger to form a rectangular package of compacted material. Knives positioned on the plunger sever the crop material at the juncture of the baling chamber and the crop inlet as the plunger passes so that the plunger may urge the crop material rearwardly in the baling chamber to form the compressed crop package in the rearward end of the baling chamber. The package so formed is tied by a tying mechanism to complete the bale, which is then discharged from the chamber by being urged rearwardly by the next bale to be formed. Completed bales are either deposited on the ground for subsequent retrieval or they are delivered by appropriate means to a trailing wagon hitched to the back of the baler.
The tying mechanism wraps transversely spaced lengths of twine around each bale after it has reached the desired size and forms knots in the twines before the bale is discharged. Knotters are disposed above the baling chamber in a row transverse to the direction of reciprocation of the plunger. The knotters are arranged adjacent a large crossbeam of square cross section that forms part of the frame surrounding and supporting the walls of the baling chamber.
Individual lengths of twine are drawn from respective reels. At the commencement of formation of each bale, the free end of each length of twine is retained within a knotter and a run of twine extends vertically through the baling chamber from the knotter to the supply reel. As the bale grows, twine is drawn from the reel and when the bale reaches its desired size, an arcuate arm, called a needle, raises the twine from beneath the bale to the level of the knotter to form a complete loop around the bale. The knotter then ties the ends of the loop surrounding the bale, severs the loop from the remainder of the twine and retains the free end of the twine to commence the tying of the next bale.
In order to raise the twine to the level of the knotters so as to complete the loop, the needles need to pass vertically through the front end of the baling chamber. By necessity, at the time that the needles traverse the front end of the baling chamber, the chamber is full of crop material and inevitably the needles will also raise some crop material to the level of the knotters. As a consequence, crop material accumulates around the knotters and this can cause the knotters to malfunction.
It has been proposed previously to provide fans to blow away any crop material that collects around the knotters but hitherto such fans have not proved entirely effective.